1. Field of the Invention
This invention relates to fluids for traction drives, and more particularly to such traction drive fluids which can be used not only for the driving force transmitting mechanism but also for the hydraulic pressure controlling mechanism and the friction characteristics controlling mechanism of the wet clutch, of the continuously variable transmissions of traction drive type of automobiles.
2. Description of Prior Art
In the field of industrial machines, traction drive fluids have already been used in traction drive type power transmitting apparatuses which transmit power via the film of the traction drive fluids. Such traction drive fluids are required to be high in traction coefficient which indicates power transmission capability.
In recent years, extensive studies and investigations on a traction drive fluid have progressed for its use of continuously variable transmissions of automobiles. The traction drive fluids to be used for an automobile are expected to be used not only in the power transmitting mechanism but also in the hydraulic controlling mechanism and the friction characteristics controlling mechanism for the wet clutch thereof.
Automatic transmission fluid (ATF) is known as a lubricant used for the hydraulic controlling mechanism of the transmission of an automobile and the friction characteristics controlling mechanism of the wet clutch of the same. It is a well-known fact that such ATF is required to be higher in a kinematic viscosity at elevated temperatures than a certain level and superior in flowability at low temperatures for performing the role of the hydraulic controlling mechanism. It is also well known that ATF needs to be blended with additives which are excelled in friction characteristics, particularly in anti-shudder characteristics for fulfilling requirements in performing the role of the friction characteristics controlling mechanism, particularly the controlling mechanism having in addition slip controlling capabilities.
SANTOTRAC is a commercially available traction drive fluid and widely known to have an excellent power transmitting capability. Traction drive fluids to be used for automobile continuously variable transmissions are required to fulfill requirements in flowability at low temperatures and other performances, but such traction drive fluids have not been placed on the market yet.